Thanks for the replies.
When you say you like the "security" of a thumb break better, my question is why? You should not need a thumb-break if your holster/belt are providing adequate retention and yoru attire is providing adequate concealment. I'm not anti-retention-> every OWB holster I use for carry purposes has some form of active retention, mostly in the form of a thumb-break. I just don't see the need for it in an IWB holster.
It sounds like when you are talking about security you mean primarily someone grabbing the gun, correct? What I'm thinking about more is the gun falling out. For both work and play I do a lot of crouching and bending and climbing and squeezing in and out of cars, etc. I have owned guns for many years, but have never CC'd much, and am gradually getting back into it. I'm still getting used to the feel of the gun pressing against my body at different angles and in different positions. Maybe I'm worrying about a non-issue.
It does seem that the thumb strap for IWB is not offered or is even frowned upon by the different manufacturers, and probably for a reason. So I will probably abandon that criteria.
I'll look at some of the different brand suggestions. I'm personally familiar with just some of the bigger brands: Bianchi, Alessi, Galco, but I like the idea of supporting the smaller guys, as long as I don't have to wait too long.
Keep the suggestions coming!